A radial turbine is a practical device for converting influent (e.g. gas) pressure and temperature to shaft power. A radial inflow turbine employs an annular inlet surrounding a turbine wheel through which the influent under pressure is directed. To uniformly distribute the influent, vanes are disposed about the annular inlet to create nozzles. Many radial inflow turbines incorporate fixed geometry nozzle vanes, or airfoils, in an attempt to optimally guide the influent entering the rotor. In such cases the principal flow parameters, such as pressure, mass flow rate, and temperature remain in fixed proportion, and cannot be individually controlled. A variable nozzle provides an additional degree of control freedom, permitting independent control over inlet temperature, pressure, and flow through the turbine stage.
These variable nozzles are often variable through the controlled pivotal motion of the vanes. Changing the stagger angle alters the throat between the vanes and changes the flow angle entering the rotor. The pivotal vanes are typically mounted between mounting rings which are positioned in a housing to either side of the annular inlet. In one example, the vanes are rotated by a series of horizontal and vertical wheels strung together on a cable. One wheel is rotated by a motor shaft connected to a motor. This one wheel, in turn, rotates each other wheel by drawing the cable clockwise or counterclockwise around each wheel. The vanes can rotate, for instance, by being connected to the axis of the wheels that rotate in a plane parallel with the plane of the mounting ring.
In another device, each vane is attached to a rod which is positioned perpendicular to the influent flow direction. The rods, in a circumferential array, protrude through a movable annular back-wall, and are rotated by a linkage. The vanes in this assembly are adjusted in discrete movements.
These types of nozzle systems are bulky, with many duplicate parts required to adjust the vanes. The bulkiness or clumsiness of these assemblies can be problematic. The additional parts and more complicated assemblies add to the manufacturing and assembly costs. Also, with the bulky, duplicate parts, sealing the influent flow paths to increase or maintain influent pressure and velocity through the nozzles can be difficult and complicated, or it can add further to the bulkiness. Each opening from the influent flow path that accommodates a part necessary for the vane adjustment is an opening that must be sealed. Duplicate parts create additional areas that need to be sealed Furthermore, these systems are limited or devoid in their adaptability for use with various existing radial inflow turbines because the parts are not easily repositioned or resized to accommodate differently configured or differently sized turbines.
It would be advantageous to eliminate or reduce duplicate parts or simplify the nozzle adjustment mechanism.
It would be advantageous to simplify the sealing arrangements and increase the sealing integrity, efficiency, or durability.
It would be advantageous to lower costs associated with component manufacturing and system assembly.
It would be advantageous to provide a nozzle assembly that can be easily adapted for use with a variety of existing radial inflow turbines.